Breakage detection system and method of chains of a scraper conveyor

ABSTRACT

Provided is a breakage detection system and method for a scraper conveyor, wherein a speed measurement device of the detection system and a sprocket assembly of the scraper conveyor are coaxially installed. Encoders are installed on speed measurement gears of the speed measurement device. An output end of the speed measurement device is connected to an input end of a programmable logic controller (PLC). An output end of the PLC is electrically connected to an automatic alarm device and a digital display module. A power supply module is used for supplying power to the whole system.

FIELD OF THE INVENTION

The present invention relates to a broken chain detection system andmethod, particularly to a broken chain detection system and method forscraper conveyer.

BACKGROUND ART

At present, scraper conveyers are developed continuously to the trend ofheavy-duty, automation, and intellectualization. Transportation safetyis always a critical problem that must be solved, owing to limitationssuch as complex operating conditions and out-of-date detectiontechnique, etc. As one of the major components of implementing a chainsprocket drive system operation, the chain of scraper conveyer may bebroken easily owing to material factor, human factor, and uneven loaddistribution factor, etc., and thereby may result in a chain reactionand have strong impacts on equipment and production safety.

Existing broken chain detection techniques for scraper conveyers, suchas detection methods with hall elements and detection methods withpressure sensors, are susceptible to external interferences and havepoor feasibility; driving motor current detection method and tensionhydraulic cylinder pressure detection method don't support detectionmethods of partially broken chains, and have poor practicability; travelswitch and contactor detection methods may be damaged easily and havepoor reliability.

CONTENTS OF THE INVENTION

Object of the invention: In order to overcome the drawbacks in thebroken chain detection technique for scraper conveyers in the prior art,the present invention provides a broken chain detection system andmethod, which is simple, easy to use and maintain.

To achieve the object described above, the present invention employs thefollowing technical solution: A broken chain detection system forscraper conveyer, comprising a speed detector, a digital display module,an automatic warning device, and a PLC controller; the speed detector ismounted coaxially with a chain wheel assembly of a scraper conveyer,encoders are mounted on speed measuring gears of the speed detector, andare hollow shaft photoelectric increment encoders configured to measurethe rotation speeds of the speed measuring gears; output end of thespeed detector are connected to input end of the PLC controller; outputend of the PLC controller are electrically connected to the automaticwarning device and the digital display module, and the PLC controller isconfigured for data processing and program setting, and start/stopcontrol of the scraper conveyer; the digital display module is ahard-wired MAX7219 chip, and is configured to display the rotation speedof the speed detector digitally; the automatic warning device comprisesa buzzer and a flashing indicator light, for a broken chain failurepre-warning; a power supply module is provided to supply power to theentire system.

The speed detector comprises a fixed retainer cup, rolling bearings, aspacer ring, and set bolts; fixed retainer cup, spacer ring, speedmeasuring gear and set bolt; a fixed retainer cup, a spacer ring, speedmeasuring gear, and set bolts, the fixed retainer cup and the spacerring are mounted between a rolling bearing and a shaft shoulder andbetween the rolling bearings respectively, the fixed retainer cup isconfigured to position the rolling bearings, the rolling bearings andthe driving shaft are in clearance fit between them, the spacer ring isfixed by the set bolts and is configured to position the speed measuringgear, and the speed measuring gear can rotate around the driving shaft.

The two encoders are provided, the central axes of the two encoders arein the same horizontal line, and the two encoders are mounted at theouter sides of two speed measuring gears symmetrically.

The speed measuring gears have the same tooth outlines as the chainwheel, and the gear teeth of the gears and the gear teeth of the chainwheel are arranged in the same phase.

A broken chain detection method for scraper conveyer, comprising thefollowing steps:

-   a) initializing a broken chain detection system, and setting a    threshold M₀ for critical relative rotation speed difference;-   b) measuring speed with encoders: during the operation of a chain    drive system after the scraper conveyer is started, when the scraper    runs to the chain wheel assembly, a protruding part of the scraper    will poke the speed measuring gears and the chain wheel assembly of    the scraper conveyer to rotate synchronously, the encoders will    rotate along with that rotation and generate count pulses    continuously, converting the count pulses to form electrical signals    feedback, and transmit the electrical signals to the PLC controller;    the PLC controller makes data processes for the electrical signals    from the two encoders respectively according to a program setting    and thereby obtain rotation speed data of the two speed measuring    gears, and obtain a relative rotation speed difference /N/ between    the two speed measuring gears through real-time computation;-   c) controlling with a PLC program: the PLC controller compares the    numerical relationship in real time; if the data values meet /N/<M₀    at any time within 5 s, it indicates that the chain of the scraper    conveyer operates normally; if /N/>M₀ occurs at any time within 5 s,    it indicates that the scraper can't normally poke the speed    measuring gears and the chain wheel assembly of the scraper conveyer    to rotate synchronously; in that case, it is judged that a broken    chain failure has happened in the scraper conveyer, and the PLC    controller controls the automatic warning device to give off an    audible and visible warning, and shuts down the scraper conveyer for    checking; moreover, the chain broken can be judged via the digital    display module; thus, a broken chain detection cycle for the scraper    conveyer is accomplished;-   d) repeating the steps b) and c), so as to detect the broken chain    condition of the scraper conveyer in real time.

Beneficial effects: In the present invention, a broken chain failure ofa scraper conveyer is judged on the basis of a relative rotation speeddifference between two speed measuring gears that are in contact withthe scraper, warning for broken chain failure and emergency stop controlof the scraper conveyer are realized by setting a program with a PLCcontroller; moreover, the speed measuring gear with a sudden speedchange can be judged intuitively via a digital display module, andthereby chain broken can be judged, and the occurrence of a severesafety accident can be avoided. The method is simple, easy to use, hashigh reliability and high practical value.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the broken chain detection method accordingto the present invention;

FIG. 2 is a schematic installation diagram of the speed detectoraccording to the present invention;

FIG. 2-1 is a structural diagram of the speed detector according to thepresent invention;

FIG. 2-2 is a partially enlarged view of the structure shown in FIG.2-1;

FIG. 3 is a diagram of the entire detection system.

In the figures: 1—driving shaft; 2—chain wheel; 3—encoder; 4—speeddetector; 41—fixed retainer cup; 42—rolling bearing; 43—spacer ring;44—speed measuring gear; 45—set bolt

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereunder the present invention will be further detailed, with referenceto the accompanying drawings.

As shown in FIG. 2, a chain wheel 2 and a speed detector 4 are connectedon a driving shaft 1; encoders 3 are connected to speed measuring gears44 of the speed detector 4.

The broken chain detection system for scraper conveyer provided in thepresent invention comprises a speed detector 4, a digital displaymodule, an automatic warning device, and a PLC controller; the speeddetector is mounted coaxially with a chain wheel assembly of a scraperconveyer, encoders 3 are mounted on speed measuring gears 44 of thespeed detector 4, and are hollow shaft photoelectric increment encodersconfigured to measure the rotation speeds of the speed measuring gears44; output end of the speed detector 4 are connected to input end of thePLC controller; output end of the PLC controller are electricallyconnected to the automatic warning device and the digital displaymodule, and the PLC controller is configured for data processing andprogram setting, and start/stop control of the scraper conveyer; thedigital display module is a hard-wired MAX7219 chip, and is configuredto display the rotation speed of the speed detector digitally; theautomatic warning device comprises a buzzer and a flashing indicatorlight, for broken chain failure pre-warning; a power supply module isprovided to supply power to the entire system.

The speed detector comprises a fixed retainer cup 41, rolling bearings42, a spacer ring 43, speed measuring gears 44, and set bolts 45,wherein, the fixed retainer cup, spacer ring, speed measuring gears andset bolts are configured to position the speed measuring gears, thefixed retainer cup and the spacer ring are mounted between a bearing anda shaft shoulder of the driving shaft 1 and between the bearingsrespectively for positioning the bearings, the bearings and the drivingshaft 1 are in clearance fit between them, the spacer ring is fixed bythe set bolts 45 and is configured to position the speed measuring gears44, and the speed measuring gears 44 can rotate around the driving shaft1.

Two encoders are provided, the central axes of the two encoders are inthe same horizontal line, and the two encoders are mounted at the outersides of two speed measuring gears symmetrically.

The speed measuring gears 2 are welded to the driving shaft and have thesame tooth outlines as the chain wheel, and the gear teeth of the gearsand the gear teeth of the chain wheel are arranged in the same phase.

As shown in FIGS. 1, 2, and 3, a broken chain detection method forscraper conveyer, comprising the following steps:

-   a) initializing the broken chain detection system, and setting a    threshold M₀ for critical relative rotation speed difference;-   b) measuring speed with the encoders: during the operation of a    chain drive system after the scraper conveyer is started, when the    scraper runs to the chain wheel assembly, a protruding part of the    scraper will poke the speed measuring gears and the chain wheel    assembly of the scraper conveyer to rotate synchronously, the    encoders will rotate along with that rotation and generate count    pulses continuously, and converting the count pulses to form    electrical signals feedback, and transmit the electrical signals to    the PLC controller; the PLC controller makes data processes for the    electrical signals from the two encoders respectively according to a    program setting and thereby obtain rotation speed data of the two    speed measuring gears, and obtain a relative rotation speed    difference /N/ between the two speed measuring gears through    real-time computation;-   c) controlling with a PLC program: the PLC controller compares the    numerical relationship in real time; if the data values meet /N/<M₀    at any time within 5 s, it indicates that the chain of the scraper    conveyer operates normally; if /N/>M₀ occurs at any time within 5 s,    it indicates that the scraper can't normally poke the speed    measuring gears and the chain wheel assembly of the scraper conveyer    to rotate synchronously; in that case, it is judged that a broken    chain failure has happened in the scraper conveyer, and the PLC    controller controls the automatic warning device to give off an    audible and visible warning, and shuts down the scraper conveyer for    checking; moreover, the chain broken can be judged via the digital    display module; thus, a broken chain detection cycle for the scraper    conveyer is accomplished;-   d) repeating the steps b) and c), so as to detect broken chain    condition of the scraper conveyer in real time.

While the present invention has been illustrated and described withreference to some preferred embodiments, the present invention is notlimited to these. The person skilled in the art should recognize thatvarious variations and modifications can be made without departing fromthe spirit and scope of the present invention. All of such variationsand modifications shall be deemed as falling into the protected scope ofthe present invention.

The invention claimed is:
 1. A broken chain detection system for ascraper conveyer, comprising a speed detector including speed measuringgears, a digital display module, an automatic warning device, and a PLCcontroller; wherein the speed detector is mounted on a drive shaftcoaxially with a chain wheel assembly, said speed detector includingphotoelectric increment encoders mounted adjacent the speed measuringgears of the speed detector, said encoders configured to measurerotation speeds of the speed measuring gears; wherein an output of theencoders is connected to an input of the PLC controller; wherein anoutput of the PLC controller is electrically connected to the automaticwarning device and the digital display module, and the PLC controller isconfigured for a start/stop control of the scraper conveyer; wherein thedigital display module is a hard-wired MAX7219 chip, and is configuredto display the rotation speed of the speed detector digitally; whereinthe automatic warning device comprises a buzzer and a flashing indicatorlight, for broken chain failure pre-warning; and a power supply moduleis provided to supply power to the entire system; wherein, the speeddetector further comprises a fixed retainer cup, rolling hearings, aspacer ring, and set bolts, wherein the fixed retainer cup, the spacerring, the speed measuring gear, and the set bolts arc configured toposition the speed measuring gears; and wherein the fixed retainer cupand the spacer ring are mounted between a rolling bearing and a shoulderof the driving shaft and between the rolling bearings respectively, thefixed retainer cup is configured to position the rolling bearings, therolling bearings and the driving shaft have a clearance fit betweenthem, the spacer ring is fixed by the set bolts and is configured toposition the speed measuring gears, and the speed measuring gears canrotate around the driving shaft.
 2. The broken chain detection systemfor scraper conveyer according to claim 1, wherein, two encoders areprovided, wherein a central axes of the two encoders are in a samehorizontal line, and wherein the two encoders are mounted at outer sidesof two speed measuring gears symmetrically.
 3. A broken chain detectionsystem for scraper conveyer comprising a speed detector including speedmeasuring gears, a digital display module, an automatic warning device,and a PLC controller; wherein the speed detector is mounted coaxiallywith a chain wheel assembly, said speed detector including photoelectricincrement encoders mounted adjacent the speed measuring gears of thespeed detector, said encoders configured to measure rotation speeds ofthe speed measuring gears; wherein an output of the encoders isconnected to an input of the PLC controller; wherein an output of thePLC controller is electrically connected to the automatic warning deviceand the digital display module, and the PLC controller is configured fora start/stop control of the scraper conveyer; wherein the digitaldisplay module is a hard-wired MAX7219 chip, and is configured todisplay the rotation speed of the speed detector digitally; wherein theautomatic warning device comprises a buzzer and a flashing indicatorlight, for broken chain failure pre-warning; and a power supply moduleis provided to supply power to the entire system; and wherein, the speedmeasuring gears have a same tooth outline as gears of the chain wheel,and the gear teeth of the speed measuring gears and the gear teeth ofthe gears of the chain wheel are arranged in a same phase.